Evaluation of the impregnation characteristics of carbon fiber-reinforced composites using dissolved polypropylene

Owing to the many advantages of carbon fiber, such as its high strength, good electrical conductivity, and light weight, carbon fiber-reinforced thermoplastics (CFRTPs) have been used in a variety of applications. However, the use of CFRTPs in fabrics suffers a significant drawback regarding their manufacture. The molten viscosity of thermoplastic resins is extremely high compared to that of thermoset resins, which makes it difficult to impregnate thermoplastic resin into fiber bundles. Therefore, a key issue is the achievement of good impregnation of the fabric with the thermoplastic polymers. In this study, a novel sizing method using polypropylene (PP) solution impregnation was proposed to improve the degree of impregnation and the interfacial characteristics between the carbon fabric and PP matrix. After impregnation, the carbon fibers were dried by microwave, and the surface properties of the PP sized fibers were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The carbon fiber-reinforced PP (CFRPP) composites were fabricated using a film stacking method. The interlaminar shear strength (ILSS) was measured using the three point bending test. From the test results, the ILSS of the specimen reinforced with the PP sized carbon fibers after epoxy de-sizing increased by 102.4% compared to that of the specimen reinforced with the untreated carbon fibers.